1. Field
Aspects of the present disclosure relate to implantable devices and methods for treating a vessel, such as a vessel having an aneurysm (e.g., aortic aneurysm).
2. Discussion of Related Art
Patients suffering from an aneurysm in a vessel are at risk for dissection or rupture of the vessel and potentially death. In general, aneurysms may be characterized by the occurrence of an abnormal swelling or dilation in a region of a blood vessel, typically to an amount greater than 1.5 times that of normal dimensions. Such pathologic dilation of the vessel may arise due to the development of an underlying weakness, or weakening, in the wall of the vessel. For instance, an aneurysm may arise due to abnormal architecture of the vessel wall due to an insufficient amount of load-bearing protein, such as elastin, to support forces (e.g., hydrostatic pressure) within the vessel. These structural defects in cellular or connective tissue may be inherited, as in the case of Marfan syndrome (fibrillin defect), or acquired, as seen in atherosclerotic degeneration. In other cases, the vessel may have an inadequate level of vascularization for the vessel wall to be sufficiently repaired when damaged or worn.
Aortic aneurysms are classified primarily by location, as enlargement may occur anywhere along the length of the aorta. FIG. 1A depicts the inside of a human cavity 10 where blood flow from the heart 12 passes through the ascending aorta 20 and travels through a system of branch vessels leading to supply all parts of the body. FIG. 1A further illustrates the aortic arch 22 arising from the ascending aorta and leading to the descending aorta, which includes the descending thoracic aorta 30 and the abdominal aorta 40, as demarcated by the diaphragm. Renal arteries 50 leading to the kidneys are also illustrated as vessels branching off the abdominal aorta. FIG. 1B depicts dilation in the thoracic aorta 30 giving rise to a thoracic aortic aneurysm 32. Similarly, dilation of the abdominal aorta 40 is shown in FIG. 1C resulting in an abdominal aortic aneurysm 42. FIG. 2A illustrates a heart 12 where an ascending aortic aneurysm 20 has developed in the ascending aorta. In this depiction, the ascending aorta is connected to a healthy aortic root 24. In other situations, the aortic root itself may be diseased or dilated. FIG. 2B illustrates a schematic of sinuses of valsalva 21 shown as cusps of the aortic root located immediately downstream from the valve leaflets.
Aneurysms of the abdominal and descending thoracic aorta are most common; however, many people suffer from abnormal dilation of the ascending aorta, aortic arch, and aortic root as well. For example, patients with connective tissue disorders such as those with Marfan Syndrome are likely to experience abnormal aortic dilation within a typical lifespan. In Marfan patients, abnormal dilation typically begins at the aortic root but may affect other regions of the vessel as well. Similarly, patients with a bicuspid aortic valve (approximately 2% of the population), are known to exhibit abnormal dilation of the ascending aorta, likely due to a connective tissue abnormality. Abnormal aortic dilation, in turn, is a common precursor to aortic dissection or rupture. Disease of the proximal aorta (i.e., ascending aorta and root) is also frequently, although not always, associated with disease of the aortic valve, and such an association may dictate medical management. Currently, treatment of aneurysms of the ascending aorta and arch typically involves complex surgical replacement of the diseased vessel, and often involves simultaneous replacement of an abnormal aortic valve. Such a valve, despite being structurally abnormal, may not exhibit significant dysfunction or otherwise merit replacement at the time of intervention on the dilated vessel, rather the decision may be made by the surgeon to replace it prophylactically at the time of vessel surgery, under the assumption that it will eventually become dysfunctional. This decision is not without consequence, however, as the vascular grafts and bioprosthetic valves used for replacement have a limited life span. More durable, mechanical prosthetic valves require life-long anticoagulation, which also carries significant risk. Therefore, premature replacement of a valve with a prosthesis may subject the patient to risk of bleeding, and/or result in the need for additional, repeat operations of increasing complexity and morbidity over the patient's lifetime. There are few alternatives to these repeat surgical procedures currently available.